A twisting machine or a spinning machine of the standard or open-end type normally has a battery of identical spinning or twisting stations responsible for respective filaments and having respective cylindrical drive whorls all engaged tangentially by a flat belt that moves continuously. Pusher rollers tangentially oppositely engage the belt and thus press the belt with enough force against the whorls to rotate these whorls by engagement with the belt. Since the individual spinning or twisting units must be stopped and reloaded regularly such a drive is used, as the belt can be easily pushed off a single whorl by a simply actuatable roller to uncouple the respective unit from the belt.
The belt therefore must therefore be designed with two characteristics in mind: strength to transmit the considerable energy it must transfer from the main drive roll it passes over to the individual whorls and flexibility to pass around and over all the whorls and rollers without damage. The belt's strength is effectively limited by its cross-sectional size, since whatever the material used to reinforce the belt, the cumulative strength is equal to the amount used. On the other hand the belt's flexibility is largely determined by its thickness, since no matter what the material flexibility is inversely related to thickness. The obvious solution is therefore to make the belt fairly wide and relatively thin, maximizing strength while minimizing stiffness.
As a result the system generates a considerable amount of noise as the considerable surface of this belt continuously engages and disengages a plurality of rollers and whorls. The noise is so great in a large such machine that the workers changing the yarn packages must be protected from it.